Radio frequency loopback for transceivers

ABSTRACT

Methods and devices for radio frequency (RF) loopback for transceivers are described. A transceiver for communicating RF signals with a target device may transmit signals at a transmit frequency and receive signals at a (different) receive frequency. The transceiver may include a waveguide diplexer for separating and combining signals based on frequency. The transceiver may be configured to couple a loopback signal from a common port of the waveguide diplexer; the loopback signal may be based on a transmit signal. The transceiver may include a loopback translator to translate the loopback signal from the transmit frequency to the receive frequency and provide the translated loopback signal to a receiver used for receiving signals from the target device. The receiver may compare the translated loopback signal with a representation of the transmit signal to generate a compensation signal. A transmitter may use the compensation signal to adjust subsequent transmit signals.

BACKGROUND

The following relates generally to transceivers for radio frequencycommunications, and more specifically to radio frequency loopback fortransceivers.

Many communication systems include radio frequency (RF) transmissionsbetween a target device and a terminal. For example, radio frequencytransmissions are used for communications between satellites and ground-or vehicle-based terminals, and for many other types of communications.In multi-frequency communication systems, RF signals may be received bya transceiver via an antenna, frequency-multiplexed using a waveguidediplexer, and converted to digital signals using an analog-to-digitalconverter (ADC) for additional processing. RF signals may be transmittedto the target device using a reverse process.

In some cases, an RF signal transmitted at the antenna may be differentthan the intended transmit signal due to distortion introduced into thesignal along the transmit path. For example, the transmit signal may beaffected by process variations or imperfections in the transceiver'sanalog and/or RF hardware, such as in the waveguide diplexer, poweramplifiers, digital-to-analog converters (DACs), and/or filters, forexample. RF transmit signals may also be affected by transceiveroperating conditions, such as temperature. It may be desirable tocompensate for such distortion before transmitting an RF signal to atarget device.

SUMMARY

The described systems and techniques relate to improved methods,devices, and apparatuses that support satellite terminal radio frequencyloopback. Generally, the described systems and techniques enable atransceiver to perform self-testing and adjust signals to be transmittedto a target device using a loopback signal from a waveguide diplexer inthe transceiver. The loopback signal may be a feedback signal that isgenerated from an RF transmit signal in the waveguide diplexer. Afrequency-translated version of the loopback signal may be provided to areceiver in the transceiver. The receiver may compare the translatedloopback signal with a representation of the intended transmit signaland generate a compensation signal based on the comparison. Atransmitter in the transceiver may use the compensation signal to adjustsubsequent signals to be transmitted to the target device. Thus, theloopback signal may enable the transceiver to adjust transmissions tocompensate for distortion introduced into the transmit signal from thedigital domain to the RF domain.

A transceiver for communicating with a target device is described. Thetransceiver may include a waveguide diplexer having a common portcoupled to first and second individual ports, the first individual portassociated with a transmit frequency range and the second individualport associated with a receive frequency range. The transceiver mayinclude a transmitter coupled with the first individual port of thewaveguide diplexer and configured to output a transmit signal to thefirst individual port within the transmit frequency range. Thetransceiver may include a bidirectional coupler having a coupled portcoupled with the common port of the waveguide diplexer. The transceivermay include a loopback translator coupled with the coupled port andconfigured to obtain a loopback signal associated with the transmitsignal via the coupled port, and to translate the loopback signal fromwithin the transmit frequency range to within the receive frequencyrange. The transceiver may include a receiver having in input portcoupled with the second individual port of the waveguide diplexer andcoupled with the loopback translator via a loopback path, where thereceiver is configured to, in a first mode, obtain a received signalfrom the target device via the waveguide diplexer, and, in a secondmode, obtain the translated loopback signal via the loopback path andcompare the translated loopback signal to a representation of thetransmit signal to generate a compensation signal, where the transmitteris further configured to receive the compensation signal and adjust thetransmit signal based at least in part on the compensation signal.

A method for compensating transmit signals transmitted to a targetdevice is described. The method may include providing a first transmitsignal to a first individual port of a waveguide diplexer, the waveguidediplexer having a common port coupled to the first individual port and asecond individual port, the first individual port associated with atransmit frequency range and the second individual port associated witha receive frequency range. The method may include coupling a loopbacksignal associated with the first transmit signal from the common port ofthe waveguide diplexer. The method may include translating the loopbacksignal from within the transmit frequency range to within the receivefrequency range. The method may include inputting, to a receiver whilein a first mode, a receive signal from the target device via thewaveguide diplexer, and inputting, to the receiver while in a secondmode, the translated loopback signal via a loopback path. The method mayinclude comparing, in the second mode, the translated loopback signalwith a representation of the first transmit signal and adjusting asecond transmit signal based on the comparison. The method may includeproviding the second transmit signal to the first individual port of thewaveguide diplexer for transmission to the target device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of an RF communication system thatsupports satellite terminal radio frequency loopback in accordance withaspects of the present disclosure.

FIG. 2 illustrates an example of a transceiver that supports satelliteterminal radio frequency loopback in accordance with aspects of thepresent disclosure.

FIG. 3 illustrates an example of a transceiver that supports satelliteterminal radio frequency loopback in accordance with aspects of thepresent disclosure.

FIG. 4 illustrates an example of a loopback translator that supportssatellite terminal radio frequency loopback in accordance with aspectsof the present disclosure.

FIG. 5 illustrates an example of a waveguide device that supportssatellite terminal radio frequency loopback in accordance with aspectsof the present disclosure.

FIG. 6 illustrates an example of a waveguide device that supportssatellite terminal radio frequency loopback in accordance with aspectsof the present disclosure.

FIG. 7 illustrates an example of a method that supports satelliteterminal radio frequency loopback in accordance with aspects of thepresent disclosure.

DETAILED DESCRIPTION

Many communication systems use radio frequency (RF) signals forcommunications between a target device and a terminal. For example, RFsignals are used for communications between satellites and ground-basedor vehicle-based terminals, and for many other types of communications.

A terminal may include a transceiver for transmitting and receiving RFsignals to and from the target device via an antenna. In some cases, thetransceiver may be a multi-frequency transceiver that transmits RFsignals at frequencies within a first frequency range and receives RFsignals at frequencies within a second (different) frequency range. Forexample, the transceiver may transmit signals at approximately 30 GHzand may receive signals at approximately 20 GHz. Using differentfrequencies for transmitting and receiving may reduce interferencebetween transmitted and received signals and/or allow the transceiver toconcurrently transmit and receive signals.

In some cases, a multi-frequency transceiver may include a waveguidediplexer for frequency-domain multiplexing of RF signals. The waveguidediplexer may serve as a filter that separates or combines RF signalsbased on frequency. The waveguide diplexer may include three ports: afirst individual port that passes signals within a first frequency range(e.g., a transmit frequency range) and rejects signals outside of thatrange, a second individual port that passes signals within a secondfrequency range (e.g., a receive frequency range) and rejects signalsoutside of that range, and a common port coupled with the firstindividual port and second individual port that passes signals in bothfrequency ranges. The common port of the waveguide diplexer may becoupled with an antenna for transmitting and receiving signals with thetarget device.

In some cases, a receive path of a transceiver (e.g., an electrical pathalong which signals may be received from the target device) may includethe waveguide diplexer, an analog-to-digital converter (ADC) to convertthe received signal to the digital domain, and various other analogand/or digital components along the way.

Similarly, a transmit path of a transceiver may include adigital-to-analog converter (DAC) to convert a digital transmit signalto an analog transmit signal, a high-powered amplifier to amplify thetransmit signal, the waveguide diplexer, and various other analog and/ordigital components along the way.

In some cases, signals to be transmitted from the terminal to the targetdevice may be affected (e.g., distorted) by various characteristics oroperating conditions of the transceiver, such as by process variationsassociated with components in the transmit path, noise, amplitude/phasedistortions, or non-linearities introduced by components in the transmitpath, and/or temperature variations during operation, for example. Thus,the actual RF signal transmitted by a transceiver may differ from theintended transmit signal; e.g., the transmit signal generated in thedigital domain.

Some transceivers may include a feedback mechanism to compensate forsuch distortion before the signal is transmitted to the target device;e.g., to pre-adjust transmit signals before they are provided to theantenna for transmission. In some cases, the feedback mechanism mayinclude a feedback signal that is generated in the digital or analogdomain of the transceiver; that is, a feedback signal may be obtainedfrom a node in the digital or analog portion of the transmit path andmay be fed back to a processor in the transceiver. The processor mayadjust subsequent transmit signals in the digital domain based on thefeedback. This approach, however, may neglect the effect of componentsthat are downstream from the node in the transmit path. Thus, it may bedesirable to provide feedback from a node that is as close to theantenna as possible.

In some cases, a transceiver may be calibrated before it is deployed inthe field to characterize the effects of such variations. Thetransceiver may be calibrated by running a calibration test (e.g., usingseparate calibration equipment) to characterize these effects. Theresulting calibration information may be stored in the terminal toenable subsequent adjustment of signals during operation. Similarly, atransceiver may perform self-testing before it is deployed to testvarious components in the transceiver. Such one-time calibration testsand self-tests may not, however, capture dynamic effects that may arisedue to temperature variations during operation of the transceiver in thefield or due to component aging, for example. Thus, it may be desirableto enable self-test and calibration of a transceiver in the field, suchas while the transceiver is deployed and configured to communicate witha target device. Moreover, it may be desirable to enable real-timecalibration, self-test, and signal compensation while the transceiver isactively communicating with a target device.

According to various aspects, a loopback translator coupled with aloopback path to the receiver may address the dual objectives ofproviding feedback from a node that is close to the antenna and enablingcalibration and self-test in the field. For example, a transceiver mayinclude a loopback path for providing a loopback signal from thewaveguide diplexer to a receiver. The loopback signal may be a frequencytranslated version of the transmit signal that enables the transceiverto adjust the transmit signal based on feedback from the RF domain(e.g., the waveguide diplexer) rather than from the analog or digitaldomain. In this case, the loopback signal may include the effect ofcomponents in the transmit path between the digital domain and the RFdomain, thereby potentially providing a more accurate feedbackmechanism.

In some cases, the loopback signal may be obtained from the waveguidediplexer by, for example, coupling an RF transmit signal from the commonport of the waveguide diplexer to generate an analog loopback signal. Inthis case, the loopback signal may be based on the transmit signal andmay have a frequency within the transmit frequency range.

The loopback signal may be provided to a loopback translator in thetransceiver. The loopback translator may translate the loopback signalfrom within the transmit frequency range to within the receive frequencyrange, thereby generating a translated loopback signal. In some cases,the transmit frequency range may include higher frequencies than thereceive frequency range. Returning to the previous example, the loopbacktranslator may translate, for example, a coupled version of a 30 GHztransmit signal (e.g., loopback signal) to a 20 GHz translated loopbacksignal. The translated loopback signal may then be provided, via aloopback path, to a receiver in the transceiver.

The receiver may be used for receiving signals from the target device atfrequencies within the receive frequency range and may also be used forreceiving the translated loopback signal within the receive frequencyrange. The receiver may be coupled with the second individual port ofthe waveguide diplexer for receiving signals at the receive frequenciesfrom the waveguide diplexer.

In some cases, translating the loopback signal from the transmitfrequency range to the receive frequency range allows the same receiverhardware (e.g., low noise amplifier (LNA), downconverter, demodulator)to be used for receiving signals from the target device (via thewaveguide diplexer) and for receiving the translated loopback signal,thereby enabling the transceiver to compensate transmit signals in thefield without having separate receiver circuitry for receiving signalsin the transmit frequency range.

In some cases, the receiver may compare the translated loopback signalto a representation of the transmit signal on which the loopback signalis based, such as a stored version of the transmit signal. The receivermay generate a compensation signal based on the comparison and mayprovide the compensation signal to the transmitter to enable thetransmitter to adjust subsequent transmissions based on the compensationsignal.

As previously noted, the receiver may receive the translated loopbacksignal via a loopback path. In some cases, the loopback path may includea path through the waveguide diplexer; that is, the translated loopbacksignal may be “looped back” from the loopback translator through thecommon port of the waveguide diplexer to the second individual port ofthe waveguide diplexer and provided to the receiver via the secondindividual port. In this case, the path from the second individual portto the receiver may be shared by the loopback path and the receive pathsuch that the receiver can receive signals from the target device andreceive the translated loopback signal at different times using the samepath.

In some cases, a transceiver may include a second loopback path, such asa direct connection between the loopback translator and the receiver. Inthis case, the translated loopback signal may be provided to thereceiver via the second loopback path without using the receive path.

In some cases, a transceiver may include two waveguide diplexers thatmay be configured to pass the same transmit and receive frequencyranges, but may each be associated with a different signal polarization,such as a left-hand circular polarization (LHCP) or right-hand circularpolarization (RHCP). Both waveguide diplexers may be coupled with thesame antenna via a polarizer (e.g., septum polarizer), for example. Inthis case, the transceiver may also include two receivers, and may becapable of receiving two signals having substantially the same frequency(e.g., within the receive frequency range) but different polarizations.Similarly, the transceiver may be capable of transmitting via eitherLHCP or RHCP (e.g., via different waveguide diplexers). Additionally oralternatively, the transceiver may have multiple transmitters, and maybe capable of concurrently transmitting LHCP and RHCP signals withsubstantially the same frequency (e.g., within the transmit frequencyrange). The second waveguide diplexer may also be used to generate aloopback signal, and a receive signal switch matrix may be used to routethe loopback signal and signals received from the target device to anavailable receiver.

Systems and techniques for radio frequency loopback for transceivers asdescribed herein may provide many benefits. For example, transceiversdescribed herein may enable self-test and compensation of transmissionsignals while the transceiver is “on air;” e.g., while the transceiveris deployed in the field and may be actively communicating with a targetdevice. Thus, transceivers described herein may be able to compensatetransmission signals based on real-time operating conditions andmaintain calibration over time in the presence of temperature variationsand component aging. Moreover, transceivers described herein may use thesame receiver hardware for receiving a loopback signal and for receivingsignals from the target device. Such shared receiver functionality mayreduce the need for additional hardware to compensate transmissionsignals. Still further, the transceivers described herein providefeedback from the RF domain (e.g., from the waveguide diplexer), whichmay capture the effects of more components in the transmit path thanfeedback from the analog or digital domain. This technique may, in turn,enable the use of lower-cost components, such as lower-cost poweramplifiers, because any additional distortion introduced by thelower-cost components may be compensated by the transmitter.

Aspects of the disclosure are initially described in the context of anRF communication system. Aspects of the disclosure are furtherillustrated by and described with reference to simplified transceivercircuits and waveguide diplexers. Aspects of the disclosure are furtherillustrated by and described with reference to apparatus diagrams,system diagrams, and flowcharts that relate to satellite terminal radiofrequency loopback. Although described with the example that thetransmit frequency range is higher than the receive frequency range, itshould be understood that the techniques discussed above for radiofrequency loopback may be applied where the transmit frequency range islower than the receive frequency range.

FIG. 1 illustrates an example of an RF communication system 100. RFcommunication system includes a terminal device 105 that may communicatewith a target device 110 by transmitting RF transmit signals 125 andreceiving RF receive signals 130 via antenna 120 and transceiver 115. Insome cases, antenna 120 may be part of transceiver 115 and/or terminaldevice 105. In some cases, terminal device 105 may be a gateway or userterminal device that may be stationary or may be located on a vehicle,such as on an airplane or ship. In some cases, target device 110 may bea satellite.

In some cases, RF transmit signals 125 may be transmitted at a frequencywithin a transmit frequency range, and RF receive signals 130 may bereceived at a frequency within a (different) receive frequency range.

In some cases, transceiver 115 may be configured to adjust transmitsignals to compensate for distortion introduced in the transmit path byobtaining, from a waveguide diplexer in transceiver 115, a loopbacksignal associated with a transmit signal in the waveguide diplexer,translating the loopback signal from the transmit frequency range to thereceive frequency range, comparing the translated loopback signal with arepresentation of the transmit signal, and adjusting subsequent transmitsignals based on the comparison.

Additional details regarding the circuitry and operation of transceiver115 are discussed with reference to FIGS. 2 through 6.

FIG. 2 illustrates a simplified example of a transceiver 200 thatsupports satellite terminal radio frequency loopback in accordance withaspects of the present disclosure. In some examples, transceiver 200 maybe an example of transceiver 115 in RF communication system 100. In somecases, transceiver 200 may include additional components that areomitted from FIG. 2 for clarity.

Transceiver 200 includes antenna 120-a, which may be used to receive andtransmit RF signals to and from a target device as depicted in FIG. 1.Antenna 120-a may include, for example, a horn antenna or feedhorn, andsignals may be directed to antenna 120-a via a reflector (e.g.,parabolic reflector). In some cases, antenna 120-a may include a phasedarray.

Transceiver 200 includes waveguide diplexer 205. Waveguide diplexer 205has a first individual port 210 associated with a transmit frequencyrange, a second individual port 215 associated with a receive frequencyrange different than the transmit frequency range, and a common port 220coupled with the first individual port 210 and the second individualport 215 and associated with the transmit frequency range and thereceive frequency range.

The first individual port 210 may be coupled with the common port via afirst waveguide that is configured to pass signals within the transmitfrequency range and may reject signals outside of the transmit frequencyrange. The second individual port 215 may be coupled with the commonport via a second waveguide that is configured to pass signals withinthe receive frequency range and may reject signals outside of thereceive frequency range. The first and second waveguides may be coupledwith the common port via a junction (e.g., E-plane T-junction, H-planeT-junction). The common port 220 may be a waveguide that is configuredto pass signals within the transmit frequency range and the receivefrequency range and may reject signals outside of the transmit frequencyrange and receive frequency range.

The common port 220 may be a waveguide that is coupled with antenna120-a to provide signals to the antenna that are within the transmitfrequency range and to receive signals from antenna 120-a within thatare within the receive frequency range. In some cases, the firstindividual port may be used for transmitting signals to the targetdevice (e.g., via common port 220 and antenna 120-a), the secondindividual port may be used for receiving signals from the target device(e.g., via antenna 120-a and common port 220). Thus, the waveguidediplexer may be configured to enable bidirectional, multi-frequency RFcommunications with the target device. Examples of waveguide diplexer205 are further described and depicted with reference to FIGS. 5 and 6.

Transceiver 200 includes a bidirectional coupler 225 having a coupledport 230. Coupled port 230 may be coupled with common port 220 and withconductive connection 235 and may be used to couple RF signals from thecommon port onto conductive connection 235, and/or to couple analogsignals on conductive connection 235 into the common port 220. That is,coupler 225 may be used to induce (e.g., generate) an analog signal onconductive connection 235 based on an RF signal in common port 220, orto induce an RF signal in common port 220 based on an analog signal onconductive connection 235.

In some cases, coupler 225 may be a passive coupler that bidirectionallycouples signals between the common port 220 and the conductiveconnection 235 when signals are present in the common port 220 or on theconductive connection 235. In some cases, coupled port 230 may be or mayinclude a coupling hole in or on the common port 220 (or a waveguidecoupled with the common port 220) to enable bidirectional couplingbetween the common port 220 and the conductive connection 235, asdepicted in the example of FIG. 5.

In some cases, coupler 225 may couple a transmit signal from common port220 to induce a loopback signal on conductive connection 235 that isbased on the RF transmit signal in the common port 220. Because theloopback signal is based on the transmit signal, the loopback signal mayhave a frequency that is within the transmit frequency range.

Transceiver 200 includes a loopback translator 240. Loopback translator240 may be coupled with the coupled port 230 via conductive connection235 and may be configured to obtain the loopback signal via coupled port230. Loopback translator 240 may be configured to translate the loopbacksignal from a frequency within the transmit frequency range to afrequency within the receive frequency range to generate a translatedloopback signal. Loopback translator 240 may include various circuitryfor performing the frequency translation, as depicted in the example ofFIG. 4.

Transceiver 200 includes receiver 245. Receiver 245 may be coupled withsecond individual port 215 of waveguide diplexer 205 and may beconfigured to receive signals from the target device via waveguidediplexer 205. Receiver 245 may include a receive (Rx) chain 283, whichmay include various components for amplifying, filtering,downconverting, or demodulating received signals or for performing otherfunctionality. Receiver 245 may include one or more analog-to-digitalconverters (ADCs) 290 for converting signals received by receiver 245from the analog domain to the digital domain Receiver 245 may includereceiver processor 285-a for processing received signals in the digitaldomain. Receive processor 285-a may include a microprocessor,microcontroller, digital signal processor (DSP), field-programmable gatearray (FPGA), application-specific integrated circuit (ASIC), and/orother type of processing hardware. Receiver 245 may include variousother components that are not shown in FIG. 2 for clarity.

Receiver 245 may also be configured to receive the translated loopbacksignal from the loopback translator 240 via a loopback path, and tocompare the translated loopback signal with a representation of thetransmit signal on which the loopback signal is based (e.g., thetransmit signal from which the loopback signal was coupled). Therepresentation of the transmit signal may be, for example, a digitalrepresentation of the transmit signal saved by transceiver 200 forsubsequent use by receiver 245. In some cases, receiver 245 may beconfigured to generate a compensation signal based on the comparison ofthe translated loopback signal with the representation of the transmitsignal. In some cases, receiver 245 may compare the translated loopbacksignal with the representation of the transmit signal and generate thecompensation signal using receive processor 285-a, for example. Thecompensation signal may subsequently be used by a transmitter 295 intransceiver 200 to compensate (e.g., adjust) transmit signals.

In some cases, the loopback path may be or may include loopback path250. In this case, the translated loopback signal from loopbacktranslator 240 is looped back through the coupled port 230 into thecommon port 220 and provided to the receiver 245 via the secondindividual port 215.

That is, the loopback path 250 may include the common port 220 andsecond individual port 215 of the waveguide diplexer. In this case,receiver 245 may receive signals from the target device and receive thetranslated loopback signal from second individual port 215 at differenttimes, allowing transceiver 200 to perform transmit signal compensationusing existing circuitry. However, in this case, transceiver 200 may notbe able to perform signal compensation while receiver 245 is activelyreceiving signals from the target device, because the loopback signaland receive signals from the target device would interfere with eachother (e.g., second individual port 215 may already be in use).

In some cases, transceiver 200 may include conductive connection 260 toprovide a second loopback path 255 from loopback translator 240 toreceiver 245. Loopback path 255 may enable loopback translator 240 toprovide a translated loopback signal to receiver 245 without loopingback through waveguide diplexer 205 and without using second individualport 215.

In this case, transceiver 200 may include switch 265 to enable receiver245 to selectively receive signals via either loopback path 255 or viasecond individual port 215. That is, receiver 245 may selectivelyreceive signals received from the target device (via second individualport 215), or the translated loopback signal (via conductive connection260).

Switch 265 may include a first input port 270 coupled with conductiveconnection 260 and a second input port 275 coupled with secondindividual port 215. Switch 265 may include an output port 280 coupledwith an input port 250 of receiver 245. Switch 265 may be configured toselect input port 270 or input port 275 for coupling with output port280.

For example, if switch 265 selects input port 270, switch 265 mayestablish an electrical connection between conductive connection 260 andreceiver 245. Thus, switch 265 may select input port 270 to provide atranslated loopback signal to receiver 245 by establishing loopback path255.

For example, if switch 265 selects input port 275, switch 265 mayestablish an electrical connection between second individual port 215and receiver 245. Thus, switch 265 may select input port 275 to providea signal received from the target device to receiver 245, or to providethe translated loopback signal to receiver 245 by establishing loopbackpath 250.

In some cases, transceiver 200 may include LNA 252 between the secondindividual port 215 and the receiver 245 for amplifying a signalreceived from the target device or the translated loopback signal (e.g.,prior to switch 265 or Rx chain 283).

In some cases, transceiver 200 (or portions of transceiver 200, such asswitch 265, receiver 245, coupler 225, and/or loopback translator 240)may be configured to operate in either a first mode associated withreceiving signals from the target device or in a second mode associatedwith receiving the translated loopback signal to perform transmit signalcompensation. For example, in some cases, transceiver 200 may include acontroller 281 that may configure transceiver 200 (or portions oftransceiver 200, such as switch 265, receiver 245, coupler 225, and/orloopback translator 240) to operate in the first mode or the second modeby providing various control signals to switch 265, receiver 245,coupler 225, loopback translator 240, and/or to other components intransceiver 200 to cause transceiver 200 to operate in the first mode orthe second mode.

Thus, receiver 245 may be configured to, in the first mode, receive asignal received from the target device, and to, in the second mode,receive the translated loopback signal from the loopback translator 240(e.g., via loopback path 250 or loopback path 255). For example,loopback translator 240 may be configured to, in the second mode, inputthe translated loopback signal to the common port 220 of the waveguidediplexer 205 via coupler 225. Alternatively, when present, switch 265may be configured to output to receiver 245, in the first mode, a signalreceived from the target device (e.g., by selecting input port 275), andto output to the receiver, in the second mode, the translated loopbacksignal (e.g., by selecting port 270 to select loopback path 255, or byselecting input port 275 to select loopback path 250.

In some cases, receiver 245 may be configured to, in the second mode,obtain the translated loopback signal and/or compare the translatedloopback signal with the representation of the transmit signal uponwhich the loopback signal is based. Receiver 245 may be configured togenerate a compensation signal based on the comparison of the translatedloopback signal with the representation of the transmit signal.

In some cases, receiver 245 may be configured to enter the second modeperiodically to receive the translated loopback signal from the loopbacktranslator. That is, receiver 245 may be configured to receive theloopback signal periodically, at predetermined time intervals, such asfor periodic self-test or calibration. In some cases, transceiver 200may store calibration values associated with the self-test orcalibration, which may subsequently be used to adjust transmit signalsor for diagnostic purposes.

In some cases, receiver 245 may be configured to enter the second modebased on the scheduling of downlink communications from the targetdevice (e.g., availability of receiver 245 to receive a translatedloopback signal). For example, receiver 245 may be configured to enterthe second mode at times when receiver 245 is not receiving a signalfrom the target device and therefore may be able to obtain thetranslated loopback signal via loopback path 250.

In some cases, receiver 245 may be configured to enter the second modein response to receiving a command or a trigger. For example, receiver245 may receive a command from, e.g., processor 285-a or 285-b oranother source specifying that receiver 245 should perform a self-testor calibration routine, and receiver 245 may respond to receiving thecommand by entering the second mode to obtain the translated loopbacksignal, compare the translated loopback signal with the representationof the transmit signal, and generate a compensation signal. Additionallyor alternatively, a trigger indicating that receiver 245 should enterthe second mode may be identified in response to detecting a change intransceiver operating conditions, such as a change in temperature,location, time of day, or other operating condition. In some cases,receiver 245 may be configured to enter the second mode based on atrigger and receiver availability (e.g., entering the second mode at anext available time period after a trigger).

In some cases, receiver 245 may compare the translated loopback signalwith the representation of the transmit signal by comparing, forexample, the frequency, phase, polarity, and/or power of the twosignals. In some cases, the compensation signal may be based on thecomparison, and may include an indication of the difference infrequency, phase, polarity, and/or power of the two signals, such as anindication of an amount of the difference(s), a sign of thedifference(s) (e.g., positive or negative), etc. In some cases, thecompensation signal may include an indication of an amount by which toadjust transmit signals, such as an amount of frequency, phase, orpower.

In some cases, the compensation signal may be provided to transmitter295 to enable transmitter 295 to adjust transmit signals based on thecompensation signal.

Transmitter 295 may be coupled with receiver 245 and with firstindividual port 210 of waveguide diplexer 205. Transmitter 295 may beconfigured to output transmit signals (e.g., signals to be transmittedto a target device) via output port 251 to first individual port 210.Transmitter 295 may be configured to output the transmit signals at afrequency within the transmit frequency range, for example.

Transmitter 295 may include transmit processor 285-b for adjustingtransmit signals based on the compensation signal. Transmit processor285-b may include a microprocessor, microcontroller, DSP, FPGA, ASIC,and/or other type of processing hardware. In some cases, transmitprocessor 285-b may be coupled with receive processor 285-a. In somecases, transmit processor 285-b may share some or all of its processinghardware with receive processor 285-a. In some cases, transmit processor285-b may be the same processor as receive processor 285-a.

Transmitter 295 may include one or more digital-to-analog converters(DACs) 292 for converting digital signals to analog signals. Transmitter295 may include a transmit chain 293, which may include variouscomponents for upconverting and/or modulating signals to be transmittedor for performing other functionality.

In some cases, transmitter 295 may include a power amplifier (PA) 297for amplifying the adjusted transmit signal; e.g., for amplifying thepower of the transmit signal after transmitter 295 has adjusted thetransmit signal. Power amplifier 297 may be coupled (e.g., via outputport 251) with the first individual port 210 of waveguide diplexer 205.Transmitter 295 may include various other components that are not shownin FIG. 2 for clarity.

Transmitter 295 may be configured to adjust transmit signals in avariety of manners, based on the compensation signal. For example,transmitter 295 may be configured to adjust transmit signals byadjusting the frequency, phase, or polarity of the transmit signals tocompensate for distortion introduced in the transmit path as identifiedby comparing the translated loopback signal and the transmit signal.

In some cases, the transmit signal may be modulated using, for example,quadrature amplitude modulation (QAM) or another modulation scheme. Inthis case, the signal may be transmitted by transmitting symbols (e.g.,QAM symbols) at a particular symbol rate, where the symbol rate is thenumber of symbols transmitted per unit time. In some cases, transmitter295 may be configured to adjust transmit signals by adjusting the symbolrate of the transmit signals based on the compensation signal. Forexample, the transmitter 295 may increase or decrease the symbol rate ofthe transmit signals depending on the amount of distortion introducedinto the transmit signal.

In some cases, transmitter 295 may be configured to adjust transmitsignals by adjusting the slew rate of the transmit signals based on thecompensation signal. The slew rate may be the rate at which a signaltransitions from a high voltage to a low voltage (or vice versa); thatis, the slew rate may represent the slope of the transition between highand low voltages.

In some cases, transmitter 295 may be configured to adjust transmitsignals by adjusting a frequency-dependent gain slope, afrequency-dependent phase variation, a time-dependent transientamplitude, a time-dependent transient phase, a frequency and amplitudedependent amplitude modulation, and/or a frequency and amplitudedependent phase modulation.

In some cases, transmitter 295 may be configured to adjust transmitsignals by adjusting the transmit power of the transmit signals based onthe compensation signal.

FIG. 3 illustrates a simplified example of a transceiver 300 thatsupports satellite terminal radio frequency loopback in accordance withaspects of the present disclosure. In some examples, transceiver 300 maybe an example of transceiver 115 in RF communication system 100. In somecases, transceiver 300 may include additional components that areomitted from FIG. 3 for clarity.

Transceiver 300 may depict an example of a transceiver that includes twowaveguide diplexers and two receivers to enable transceiver 300 toconcurrently receive, using the two receivers, two signals from a targetdevice and/or to concurrently receive a signal from a target device anda translated loopback signal from a loopback translator.

Transceiver 300 includes antenna 120-b, which may be used to receive andtransmit RF signals to and from a target device as depicted in FIG. 1.Antenna 120-b may include, for example, a horn antenna or feedhorn, andsignals may be directed to antenna 120-b via a reflector (e.g.,parabolic reflector).

Transceiver 300 includes two waveguide diplexers 205-a, 205-b. Waveguidediplexers 205-a, 205-b may be examples of waveguide diplexer 205described with reference to FIG. 2 and may operate in a similar mannerEach waveguide diplexer 205-a, 205-b has a first individual port 210-a,210-b associated with a transmit frequency range, a second individualport 215-a, 215-b associated with a receive frequency range differentthan the transmit frequency range, and a common port 220-a, 220-bcoupled with the first individual port 210-a, 210-b and the secondindividual port 215-a, 215-b and associated with the transmit frequencyrange and the receive frequency range.

Transceiver 300 includes polarizer 310 for dividing or combining signalsbased on their polarization (e.g., RHCP, LHCP, linear polarizations).Polarizer 310 may enable a single antenna 120-b to be used with the twowaveguide diplexers 205-a, 205-b by dividing received waves based ontheir polarization and by combining signals having differentpolarizations for transmission.

Polarizer 310 may be coupled with both waveguide diplexers 205-a, 205-b.Polarizer 310 may receive RF signals from a target device having a firstand/or second polarization and may route signals of the firstpolarization (e.g., RHCP, first linear polarization) to waveguidediplexer 205-a and route signals of the second polarization (e.g., LHCP,second linear polarization) to waveguide diplexer 205-b, for example.Similarly, polarizer 310 may receive signals from waveguide diplexer205-a and may polarize signals from waveguide diplexer 205-a to have thefirst polarization for transmission to the target device. Polarizer 310may receive signals from waveguide diplexer 205-b and may polarizesignals from waveguide diplexer 205-b to have the second polarizationfor transmission to the target device. In some cases, polarizer 310 maybe a septum polarizer that may transfer energy of a received signalcorresponding to different orthogonal basis polarizations (e.g., RHCP,LHCP) to different divided waveguides and convert component signalstravelling from the different divided waveguides to the orthogonal basispolarizations in a combined polarization signal, for example.

Transceiver 300 includes bidirectional couplers 225-a, 225-b, each ofwhich has a coupled port 230-a, 230-b. Couplers 225-a, 225-b may each bean example of a coupler 225 described with reference to FIG. 2.

Each coupled port 230-a, 230-b may be coupled with a common port 220-a,220-b of a waveguide diplexer 205-a, 205-b and with a conductiveconnection 235-a, 235-b and may be used to couple RF signals from therespective common port 220-a, 220-b onto the conductive connection235-a, 235-b, and/or to couple analog signals on conductive connection235-a, 235-b into an RF signal in the respective common port 220-a,220-b. That is, couplers 225-a, 225-b may each be used to induce (e.g.,generate) an analog signal on a respective conductive connection 235-a,235-b based on an RF signal in common port 220-a, 220-b, or to induce anRF signal in common port 220-a, 220-b based on an analog signal onconductive connection 235-a, 235-b.

In some cases, each coupler 225-a, 225-b may be configured to couple atransmit signal from common port 220-a, 220-b to induce a loopbacksignal on conductive connection 235-a, 235-b that is based on an RFtransmit signal in the common port 220-a, 220-b. Thus, transceiver 300may support loopback signals from either waveguide diplexer 205-a,205-b.

Transceiver 300 includes loopback translator 240-a. Loopback translator240-a may be an example of loopback translator 240 described withreference to FIG. 2. Loopback translator 240-a may be coupled with eachcoupled port 230-a, 230-b via respective conductive connection 235-a,235-b and may be configured to obtain the loopback signal via eithercoupled port 230-a, 230-b. Loopback translator 240-a may be configuredto translate the loopback signal from a frequency within the transmitfrequency range to a frequency within the receive frequency range togenerate a translated loopback signal.

Transceiver 300 includes two receivers 245-a, 245-b for receivingsignals within the receive frequency range, and transceiver 300 includesa receive signal switch matrix 315 for routing the signals to thereceivers 245-a, 245-b. In some cases, receive signal switch matrix 315may enable either receiver 245-a or 245-b to receive signals from eitherwaveguide diplexer 205-a or 205-b. Such signals may be signals receivedfrom a target device and/or translated loopback signals received from aloopback translator 240-a by looping the translated loopback signal backthrough one of the waveguide diplexers 205-a, 205-b. That is, receivesignal switch matrix may be configured to input, to one receiver 245-a,a signal received from the target device while inputting, to the otherreceiver 245-b, a translated loopback signal.

In some cases, transceiver 300 (or portions of transceiver 300, such assome or all of receive signal switch matrix 315, receiver 245-a, 245-b,coupler 225-a, 225-b, and/or loopback translator 240-a) may beconfigured to operate in either a first mode associated with receivingsignals from a target device or in a second mode associated withreceiving a translated loopback signal to perform transmit signalcompensation, as described with reference to FIG. 2.

For example, one of receivers 245-a, 245-b may be configured to, in thesecond mode, receive a translated loopback signal, compare thetranslated loopback signal with a representation of the transmit signalfrom which the loopback signal was coupled, and generate a compensationsignal. In some cases, in the second mode, one receiver 245 may receivesignals from a target device while the other receiver 245 receives andcompares the translated loopback signal.

In some cases, the compensation signal may be provided to a transmitter295-a in transceiver 200 to enable transmitter 295-a to adjust transmitsignals based on the compensation signal, as described with reference toFIG. 2. Transmitter 295-a may be coupled with first individual ports210-a, 210-b of waveguide diplexers 205-a, 205-b via switch 265-c andmay be configured to output transmit signals (e.g., signals to betransmitted to a target device) to first individual ports 210-a, 210-b.Transmitter 295-a may be configured to output the transmit signals at afrequency within the transmit frequency range, for example. As discussedwith reference to FIG. 2, transmitter 295-a may be configured to adjusttransmit signals in a variety of manners, based on the compensationsignal.

Receive signal switch matrix 315 includes two splitters 305-a, 305-b andtwo switches 265-a, 265-b. Each splitter 305-a, 305-b has an input port320-a, 320-b that is coupled with a second individual port 215-a, 215-bof a waveguide diplexer 205-a, 205-b. In some cases, input ports 320-a,320-b may be input ports of the receive signal switch matrix 315, forexample.

Each splitter 305-a, 305-b may be configured to route separate instancesof (e.g., split) a signal received via a waveguide diplexer 205-a, 205-bto receivers 245-a, 245-b via various input ports 275 of switches 265-a,265-b.

Each switch 265-a, 265-b has an output port 280-a, 280-b coupled with areceiver 245-a, 245-b. In some cases, output ports 280-a, 280-b may beoutput ports of the receive signal switch matrix 315, for example. Eachswitch 265-a, 265-b may be configured to selectively provide signals tothe corresponding receiver 245-a, 245-b by selecting an input port 275to couple the selected input port 275 with the output port 280 of theswitch 265.

Switch 265-a may include input port 270-a for receiving a translatedloopback signal from loopback translator 240-a via conductive connection260-a. Thus, switch 265-a may enable receiver 245-a to selectivelyreceive a loopback signal via a direct loopback path, in a mannersimilar to that described for loopback path 255 in FIG. 2.

In transceiver 300, there may be multiple loopback paths betweenloopback translator 240-a and receivers 245-a, 245-b. For example, atranslated loopback signal may be looped back, via conductive connection235-a or 235-b, through either waveguide diplexer 205-a or waveguidediplexer 205-b (e.g., by coupling the translated loopback signal backinto the common port 220-a, 220-b via coupled port 230-a, 230-b). Thetranslated loopback signal may then be provided to receiver 245-a orreceiver 245-b via second individual port 215-a, 215-b and receivesignal switch matrix 315. As previously noted, transceiver 300 may alsoinclude a direct loopback path from loopback translator 240-a toreceiver 245-a via switch 265-a.

Receivers 245-a, 245-b may be configured to receive a translatedloopback signal from the loopback translator 240-a via a loopback path,and to compare the translated loopback signal with a representation ofthe transmit signal on which the loopback signal is based (e.g., thetransmit signal from which the loopback signal was coupled). Theinclusion of two waveguide diplexers 205-a, 205-b and two receivers245-a, 245-b may provide transceiver 300 with additional flexibility forrouting signals received from the target device and for routing loopbacksignals, thereby providing more flexibility for transceiver 300 toperform self-test, calibration, and transmission signal adjustment whiletransceiver 300 is communicating with a target device. For example,transceiver 300 may be able to use one receiver 245-a to perform signalcompensation while the other receiver 245-b is actively receivingsignals from a target device.

Although not shown in FIG. 3 for clarity, in some cases, transceiver 300may include LNAs between the second individual ports 215-a, 215-b andthe receivers 245-a, 245-b for amplifying a signal received from thetarget device or the translated loopback signal, such as depicted inFIG. 2. In some cases, transmitter 295-a may include a power amplifieras depicted in FIG. 2. In some cases, receivers 245-a, 245-b may becoupled with a processor in transceiver 300 in a manner similar to thatshown in FIG. 2 and may be configured to compare the translated loopbacksignal with the representation of the transmit signal and generate thecompensation signal via the processor; e.g., by providing the translatedloopback signal to the processor.

FIG. 4 illustrates an example of a loopback translator 400 that supportssatellite terminal radio frequency loopback in accordance with aspectsof the present disclosure. In some examples, loopback translator 400 maybe an example of loopback translator 240, 240-a as depicted in FIGS. 2and 3. Loopback translator 400 may include various additional componentsthat are not shown in FIG. 4 for simplicity. Moreover, otherimplementations of a loopback translator may also be used within atransceiver, such as transceiver 200, 300, without departing from thescope of the present disclosure.

Loopback translator 400 includes conductive connection 235-c that may beused for receiving a loopback signal from a waveguide diplexer, such aswaveguide diplexer 205, 205-a, and/or for providing a translatedloopback signal to the waveguide diplexer. Conductive connection 235-cmay be an example of conductive connection 235, 235-a as depicted inFIGS. 2 and 3.

Loopback translator 400 may include combiner/divider 405-a.Combiner/divider 405-a may be coupled with conductive connection 235-cand configured to couple to conductive connection 235-c to filter 415-aand filter 415-b (potentially via switches 410 and 435, as described inmore detail below). Combiner/divider 405-a may be configured to split aninput signal into two output signals and/or to combine two input signalsinto a single output signal.

Filter 415-a may be configured to filter a loopback signal received via,for example, conductive connection 235-c. In some cases, filter 415-amay be associated with the transmit frequency range. For example, insome cases, the loopback signal may have a frequency within the transmitfrequency range, and filter 415-a may be or include a band pass filterthat may filter the loopback signal based on a pass band that is roughlycentered on a center frequency of the transmit frequency range. In somecases, filter 415-a may be or include a high pass filter that may filterthe loopback signal by passing signals having frequencies that are abovea cutoff frequency, where the transmit frequency range is above thecutoff frequency.

Loopback translator 400 includes RF loopback attenuator 420. RF loopbackattenuator 420 may be configured to attenuate (e.g., decrease) a powerassociated with the loopback signal before the loopback signal istranslated to a frequency within the receive frequency range.

Loopback translator 400 includes local oscillator 425 and mixer 430 fortranslating the loopback signal from a frequency within the transmitfrequency range to a frequency within the receive frequency range toprepare the loopback signal for reception by a receiver, such asreceiver 245. Local oscillator 425 may generate a sinusoidal oscillatorsignal. Mixer 430 may be coupled with RF loopback attenuator 420 andlocal oscillator 425, and may be configured to generate, based on theoscillator signal and the loopback signal, a translated loopback signalhaving a frequency that is within the receive frequency range. In somecases, the local oscillator 425 may provide an oscillator signal havinga frequency representing the difference between a center frequency ofthe transmit signals and the center frequency of the receive signals.Where the transmit frequency is greater than the receive frequency, themixer 430 may be used to downconvert the loopback signal at the transmitfrequency to the translated loopback signal within the receive frequencyrange. Where the transmit frequency is lower than the receive frequency,the mixer 430 may be used to upconvert the loopback signal at thetransmit frequency to the translated loopback signal within the receivefrequency range.

Loopback translator 400 includes filter 415-b coupled with mixer 430.Filter 415-b may be configured to filter the signal received from mixer430 to pass the translated loopback signal. Filter 415-b may beassociated with the receive frequency range. In some cases, filter 415-bmay include a band pass filter to filter signals based on a pass bandthat is roughly centered on a center frequency of the receive frequencyrange. In some cases, filter 415-b may include a low pass filter thatmay filter signals by passing signals that are below a cutoff frequency,where the receive frequency range is below the cutoff frequency. In somecases, filter 415-b is configured to output the translated loopbacksignal.

Filter 415-b may be coupled with conductive connection 235-c (e.g., viacombiner/divider 405-a and/or switch 435) to provide the translatedloopback signal to a receiver. That is, in some cases, a loopback signalreceived from a waveguide diplexer may traverse a frequency translationpath 440 in loopback translator 400 that includes filter 415-a, RFloopback attenuation 420, mixer 430, and filter 415-b to generate andoutput the translated loopback signal as an output of filter 415-b. Thetranslated loopback signal may then be provided to a receiver, such asreceiver 245-a, 245-b described with reference to FIGS. 2 and 3.

In some cases, loopback translator 400 may include conductive connection260-b, which may be configured to provide a translated loopback signalto a receiver without looping back through a waveguide diplexer.Conductive connection 260-b may be an example of conductive connections260, 260-a described with reference to FIGS. 2 and 3.

In some cases, if loopback translator includes conductive connection260-b, loopback translator may include switch 435 to select a loopbackpath by which to provide the translated loopback signal to a receiver.That is, switch 435 may select a loopback path that loops back through awaveguide diplexer (e.g., via combiner/divider 405-a and conduciveconnection 235-c) by selecting a first output or may select a loopbackpath that provides the translated loopback signal directly to thereceiver (e.g., via conductive connection 260-b) by selecting a secondoutput.

For transceivers that include two waveguide diplexers such astransceiver 300 of FIG. 3, loopback translator 400 may includeadditional circuitry (e.g., conductive connection 235-d,combiner/divider 405-b, switch 410, and/or switch 435) to enableloopback translator 400 to communicate loopback signals and translatedloopback signals with two waveguide diplexers and two receivers, forexample. In this case, loopback translator 400 may depict an example ofa loopback translator that may be used in a transceiver having twowaveguide diplexers, such as transceiver 300 depicted in FIG. 3.

For example, conductive connection 235-d may be used for receiving aloopback signal from a second waveguide diplexer, such as waveguidediplexer 205-b, and/or for providing a translated loopback signal to thesecond waveguide diplexer. Conductive connection may be an example ofconductive connection 235-b described with reference to FIG. 3.

Combiner/divider 405-b may be coupled with conductive connection 235-dand may be configured to couple conductive connection 235-d to switch410 and switch 435. Combiner/divider 405-b may be configured to split aninput signal into two output signals and/or to combine two input signalsinto a single output signal.

Switch 410 may be coupled with conductive connections 235-c, 235-d(e.g., via combiner/dividers 405-a and/or 405-b). Switch 410 may also becoupled with filter 415-a and may be configured to route a loopbacksignal received via either conductive connection 235-c (e.g., receivedfrom a first waveguide diplexer) or conductive connection 235-d (e.g.,received from a second waveguide diplexer) to filter 415-a.

Similarly, switch 435 may be coupled with conductive connections 235-c,235-d (e.g., via combiner/dividers 405-a, 405-b) and with conductiveconnection 260-b, if present. Switch 435 may also be coupled with filter415-b and may be configured to route a translated loopback signal toconductive connection 260-b, to conductive connection 235-c (e.g., to afirst waveguide diplexer) or to conductive connection 260-c (e.g., to asecond waveguide diplexer).

Thus, loopback translator 400 may, in some cases, be configured toreceive loopback signals from either of two waveguide diplexers, route areceived loopback signal through a frequency translation path 440 totranslate the loopback signal to a translated loopback signal, and routethe translated loopback signal to either of two receivers by routing thetranslated loopback signal back through either of the two waveguidediplexers or directly to a receiver.

In some cases, the inclusion of switch 410 and switch 435 may enable atransceiver 300 (e.g., a controller in transceiver 300) to select acoupler 225-a or coupler 225-b for the loopback path based on variousoptimization and scheduling criteria. Such criteria may include, forexample, whether a waveguide diplexer 205-a, 205-b associated with acoupler 225-a, 225-b is currently receiving a signal from the targetdevice, whether providing the translated loopback signal to coupler225-a, 225-b is likely to cause interference with other signals atwaveguide diplexer 205-a, 205-b, etc.

FIG. 5 illustrates an example of a waveguide device 500 that supportssatellite terminal radio frequency loopback in accordance with aspectsof the present disclosure.

Waveguide device 500 includes waveguide diplexer 205-c, which may be anexample of waveguide diplexer 205, 205-a, 205-b described with referenceto FIGS. 2 and 3. Waveguide diplexer 205-c may be designed to passcertain frequencies of an RF signal and reject other frequencies. Thatis, in some cases, the waveguides coupled with the ports of waveguidediplexer 205 may be configured to act as filters for RF signals, asshown in FIG. 5.

Waveguide diplexer 205-c includes first individual port 210-c, which maybe associated with communicating (e.g., transmitting) signals in thetransmit frequency range. For example, waveguide diplexer 205-c mayinclude Tx filter 535, which may be a highpass, lowpass, or bandpassfilter. Waveguide diplexer includes second individual port 215-c, whichmay be associated with communicating (e.g., receiving) signals in thereceive frequency range. For example, waveguide diplexer 205-c mayinclude Rx filter 525, which may be a highpass, lowpass, or bandpassfilter. Where the transmit frequency range is higher than the receivefrequency range, for example, the Tx filter 535 may be a highpass orbandpass filter, and the Rx filter 525 may be a lowpass or bandpassfilter. Waveguide diplexer includes common port 220-c, which may beassociated with communicating signals in both the transmit frequencyrange and receive frequency range. Common port 220-c may be coupled withfirst individual port 210-c and with second individual port 215-c (e.g.,via a waveguide junction). Common port 220-c may be coupled with anantenna.

Waveguide device 500 includes coupled port 230-c, which may be anexample of coupled port 230, 230-a, or 230-b described with reference toFIGS. 2 and 3. Waveguide device includes coupling hole 505, which may bea hole in a waveguide associated with common port 220-c. Coupled port230-c and coupling hole 505 may be included in or may be an example of abidirectional coupler, such as coupler 225, 225-a, 225-b described withreference to FIGS. 2 and 3.

Coupling hole 505 may be used to couple signals between common port220-c and a conductive connection (e.g., conductive connection 235) thatis coupled with coupling hole 505 via coupled port 230-c. In some cases,coupling hole 505 may couple signals by coupling power or energy betweenthe conductive connection and the common port 220-c.

In some cases, coupling hole 505 may be used to couple a loopback signalonto a conductive connection from a transmit signal in common port220-c, such as to provide a loopback signal to a loopback translator. Insome cases, coupling hole 505 may be used to couple a translatedloopback signal from the conductive connection into the common port220-c, such as to provide the translated loopback signal to a receivervia the loopback path 250 of FIG. 2, for example.

In some cases, coupling hole 505 may be configured to provide aparticular coupling value, which may represent a percentage of energy orpower that is coupled. In some cases, it may be desirable to designcoupling hole 505 such that the coupling value is low enough not todisturb transmit signals in common port 220-c but high enough to providea sufficiently strong loopback signal, for example. In some cases, thesize or location of coupling hole 505 may be selected to provide lowenough coupling (e.g., a low coupling value) to avoid disturbingtransmit signals while providing high enough coupling to reduce thevariability of the coupled signal.

For example, in some cases, the size of coupling hole 505 may beconfigured such that coupling hole 505 has a cutoff frequency above thetransmit or receive frequency ranges and therefore couples evanescentmode energy without coupling propagating mode energy. For example,coupling hole 505 may be a circular hole that is small enough to have acutoff frequency higher than signals in common port 220-c. Thistechnique may reduce the impact of the coupler on transmit signals, forexample.

In some cases, coupling hole 505 may be located in an E-plane wall ofcommon port 220-c. An E-plane may be a plane associated with an electricfield vector, for example, which may be orthogonal to an H-plane that isa plane associated with a magnetic field vector. In general, the centerof an E-plane wall may have little to no current, and therefore thecoupling hole 505 may be offset from the center of the E-plane wall toprovide better coupling, and a position, size, and cross-sectional shapeof the coupling hole 505 may be selected to provide a desired amount ofcoupling.

In some cases, coupled port 230-c may be part of waveguide diplexer205-c or may be a separate device. For example, common port 220-c may becoupled with an additional waveguide for transmitting and receivingsignals, and coupled port 230-c may be coupled with the additionalwaveguide.

FIG. 6 illustrates an example of a waveguide device 600 that supportssatellite terminal radio frequency loopback in accordance with aspectsof the present disclosure. In some examples, waveguide device 600 mayimplement aspects of waveguide diplexer 205, 205-a, 205-b and coupler225, 225-a, 225-b as depicted in FIGS. 2 and 3.

Waveguide device 600 includes waveguide diplexer 205-d having a firstindividual port 210-d, second individual port 215-d, and common port220-d. Waveguide diplexer 205-d may be an example of waveguide diplexer205-c as described with reference to FIG. 5, for example. Waveguidedevice 600 includes microstrip 605, which may be a conductive elementthat spans coupling hole 505. Microstrip 605 may be separated from thecoupling hole 505 by a dielectric layer, for example. Microstrip 605 maybe part of a coupler, such as coupler 225, and may be used to conduct(e.g., couple) RF energy onto a conductive connection, such asconductive connection 235, 235-a, 235-b described with reference toFIGS. 2 and 3. Microstrip 605 may be a shielded microstrip, for examplecovered by a housing (not shown) shielding the top of microstrip 605.Microstrip 605 may also include one or more impedance matching stubs(not shown), which may be located on one or both sides of coupling hole505.

FIG. 7 illustrates an example of a method 700 that supports satelliteterminal radio frequency loopback in accordance with aspects of thepresent disclosure. In some examples, method 700 may implement aspectsof RF communication system 100.

Block 705 may include providing a first transmit signal to a firstindividual port of a waveguide diplexer, such as first individual port210, 210-a, 210-b of waveguide diplexer 205, 205-a, 205-b, for example.The waveguide diplexer may include a common port coupled to the firstindividual port and a second individual port, such as common port 220,220-a, 220-b, for example, which is coupled with first individual port210, 210-a, 210-b and second individual port 215, 215-b, 215-c,respectively. The first individual port may be associated with atransmit frequency range and the second individual port may beassociated with a receive frequency range. The first transmit signal maybe within the transmit frequency range, for example.

Block 710 may include coupling a loopback signal associated with thefirst transmit signal from the common port of the waveguide diplexer. Insome cases, the loopback signal may be coupled from the common port ofthe waveguide diplexer using a bidirectional coupler, such as coupler225, 225-a, 225-b, for example.

Block 715 may include translating the loopback signal from within thetransmit frequency range to within the receive frequency range. In somecases, the loopback signal is translated from within the transmitfrequency range to within the receive frequency range by a loopbacktranslator, such as loopback translator 240, 240-a, 240-b, for example.

Block 720 may include inputting, to a receiver while in a first mode, areceive signal from the target device via the waveguide diplexer. Insome cases, the receive signal may be input to the receiver via thesecond individual port of the waveguide diplexer and/or via a switch,such as switch 265, 265-a, that is coupled with the second individualport of the waveguide diplexer. In some cases,

Block 725 may include inputting, to the receiver while in a second mode,the translated loopback signal via a loopback path. In some cases, thetranslated loopback signal may be input to the receiver via a loopbackpath that may include the common port and second individual port of thewaveguide diplexer or may include a conductive connection such asconductive connection 260. In some cases, the translated loopback signalmay be input to the receiving via a switch, such as switch 265, that iscoupled with the second individual port of the waveguide diplexer and/orwith the conductive connection. In some cases, the switch may beconfigured to, in the second mode, establish a loopback path (e.g.,loopback path 250, 255, or another loopback path) to output thetranslated loopback signal to the receiver. In some cases, the loopbackpath may include a common port and second individual port of a waveguidediplexer. In some cases, the receive signal is input to the receiverduring a first time interval and the translated loopback signal is inputto the receiver during a second time interval.

Block 730 may include comparing, in the second mode, the translatedloopback signal with a representation of the first transmit signal. Insome cases, the receiver may compare the translated loopback signal witha representation of the first transmit signal using a receive processor,such as receive processor 285-a, for example. In some cases, therepresentation of the first transmit signal may be a digitalrepresentation that is stored by receive processor 285-a or by atransmit processor, such as transmit processor 285-b, for example.

Block 735 may include adjusting a second transmit signal based at leastin part on the comparison. The second transmit signal may be, forexample, a signal that is transmitted (or is scheduled to betransmitted) to a target device after the loopback signal has beencoupled from a previous transmit signal. That is, the loopback signalfrom the first transmit signal may be used to adjust a subsequenttransmit signal. In some cases, a transmitter, such as transmitter 295,295-a, may adjust the second transmit signal by adjusting a frequency, aphase, a polarity, a symbol rate, a slew rate, a frequency-dependentgain slope, a frequency-dependent phase variation, a time-dependenttransient amplitude, a time-dependent transient phase, a frequency andamplitude dependent amplitude-modulation, a frequency and amplitudedependent phase modulation, or a transmit power of the transmit signals.In some cases, a transmitter may be configured to adjust the secondtransmit signal using a transmit processor, such as transmit processor285-b, or using other hardware or software.

Block 740 may include providing the second transmit signal to the firstindividual port of the waveguide diplexer for transmission to the targetdevice. In some cases, the second transmitted signal is provided, by thetransmitter, to the first individual port after the second transmitsignal has been adjusted, for example. In some cases, the Informationand signals described herein may be represented using any of a varietyof different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA, or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices(e.g., a combination of a DSP and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROMor other optical disk storage, magnetic disk storage or other magneticstorage devices, or any other non-transitory medium that can be used tocarry or store desired program code means in the form of instructions ordata structures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, include CD, laser disc, optical disc,digital versatile disc (DVD), floppy disk and Blu-ray disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above are also includedwithin the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary step that is described as “based on conditionA” may be based on both a condition A and a condition B withoutdeparting from the scope of the present disclosure. In other words, asused herein, the phrase “based on” shall be construed in the same manneras the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A transceiver for communicating with a targetdevice, the transceiver comprising: a waveguide diplexer comprising acommon port coupled to first and second individual ports, the firstindividual port associated with a transmit frequency range and thesecond individual port associated with a receive frequency range; atransmitter coupled with the first individual port of the waveguidediplexer and configured to output a transmit signal to the firstindividual port within the transmit frequency range; a bidirectionalcoupler having a coupled port coupled with the common port of thewaveguide diplexer; a loopback translator coupled with the coupled portand configured to obtain a loopback signal associated with the transmitsignal via the coupled port, and to translate the loopback signal fromwithin the transmit frequency range to within the receive frequencyrange; and a receiver having in input port coupled with the secondindividual port of the waveguide diplexer and coupled with the loopbacktranslator via a loopback path, wherein the receiver is configured to,in a first mode, obtain a received signal from the target device via thewaveguide diplexer, and, in a second mode, obtain the translatedloopback signal via the loopback path and compare the translatedloopback signal to a representation of the transmit signal to generate acompensation signal, wherein the transmitter is further configured toreceive the compensation signal and adjust the transmit signal based atleast in part on the compensation signal.
 2. The transceiver of claim 1,wherein, in the second mode: the loopback translator is configured tooutput the translated loopback signal to the coupler to couple thetranslated loopback signal into the common port of the waveguidediplexer, wherein the loopback path includes a portion of the waveguidediplexer comprising the common port and the second individual port. 3.The transceiver of claim 1, further comprising: a switch having a firstinput port coupled with the second individual port of the waveguidediplexer, a second input port coupled with the loopback translator viathe loopback path, and an output port coupled with the input port of thereceiver, the switch configured to output to the receiver, in the firstmode, the received signal, and to output to the receiver, in the secondmode, the translated loopback signal.
 4. The transceiver of claim 1,wherein the waveguide diplexer is a first waveguide diplexer, thebidirectional coupler is a first bidirectional coupler, the receiver isa first receiver, and the received signal from the target device is afirst received signal, further comprising: a second waveguide diplexercomprising a common port coupled to third and fourth individual ports,the third individual port associated with the transmit frequency rangeand the fourth individual port associated with the receive frequencyrange; a second bidirectional coupler having a coupled port coupled withthe common port of the second waveguide diplexer a second receiver; anda receive signal switch matrix having a first input port coupled withthe second individual port of the first waveguide diplexer, a secondinput port coupled with fourth individual port of the second waveguidediplexer, a first output port coupled with the first receiver, and asecond output port coupled with the second receiver, and configured tooutput the first received signal or a second received signal from thetarget device on the first output port and the first received signal orthe second received signal on the second output port.
 5. The transceiverof claim 4, wherein the first receiver is configured to obtain, in thesecond mode, the translated loopback signal concurrently with the secondreceiver obtaining the first signal or the second signal via the receivesignal switch matrix.
 6. The transceiver of claim 4, wherein, in thesecond mode: the loopback translator is configured to output thetranslated loopback signal to the second coupler to couple thetranslated loopback signal into the common port of the second waveguidediplexer, wherein the loopback path includes a portion of the secondwaveguide diplexer comprising the common port and the fourth individualport.
 7. The transceiver of claim 4, further comprising: a polarizercoupled with the common ports of the first and second waveguidediplexers, the polarizer configured to divide a received wave into thefirst and second signals according to respective polarizations of thefirst and second signals in the received wave.
 8. The transceiver ofclaim 4, wherein the first receiver is configured to receive, in thesecond mode, the translated loopback signal from the loopback translatorsubstantially continuously while the transceiver is communicating withthe target device.
 9. The transceiver of claim 1, further comprising alow noise amplifier between the second individual port of the waveguidediplexer and the receiver.
 10. The transceiver of claim 1, wherein thereceiver is configured to enter the second mode periodically to receivethe translated loopback signal from the loopback translator.
 11. Thetransceiver of claim 1, wherein the receiver is configured to enter thesecond mode to obtain the translated loopback signal from the loopbacktranslator based at least in part on a scheduling of downlinkcommunications from the target device.
 12. The transceiver of claim 1,wherein the coupler comprises a coupling hole on a waveguide associatedwith the common port.
 13. The transceiver of claim 12, wherein thecoupler further comprises a microstrip spanning the coupling hole. 14.The transceiver of claim 13, wherein the microstrip is separated fromthe coupling hole by a dielectric layer.
 15. The transceiver of claim 1,wherein the transmitter comprises: a power amplifier coupled with thefirst individual port of the waveguide diplexer for amplifying theadjusted transmit signal.
 16. The transceiver of claim 1, wherein thetransmitter is configured to adjust the transmit signal by adjusting afrequency, a phase, a polarity, a symbol rate, a slew rate, afrequency-dependent gain slope, a frequency-dependent phase variation, atime-dependent transient amplitude, a time-dependent transient phase, afrequency and amplitude dependent amplitude-modulation, a frequency andamplitude dependent phase modulation, or a transmit power of thetransmit signals.
 17. A method for compensating transmit signalstransmitted to a target device, the method comprising: providing a firsttransmit signal to a first individual port of a waveguide diplexer, thewaveguide diplexer comprising a common port coupled to the firstindividual port and a second individual port, the first individual portassociated with a transmit frequency range and the second individualport associated with a receive frequency range; coupling a loopbacksignal associated with the first transmit signal from the common port ofthe waveguide diplexer; translating the loopback signal from within thetransmit frequency range to within the receive frequency range;inputting, to a receiver while in a first mode, a receive signal fromthe target device via the waveguide diplexer; inputting, to the receiverwhile in a second mode, the translated loopback signal via a loopbackpath; comparing, in the second mode, the translated loopback signal witha representation of the first transmit signal; adjusting a secondtransmit signal based at least in part on the comparison; and providingthe second transmit signal to the first individual port of the waveguidediplexer for transmission to the target device.
 18. The method of claim17, further comprising, in the second mode: coupling the translatedloopback signal into the common port of the waveguide diplexer, whereinthe loopback path includes a portion of the waveguide diplexercomprising the common port and the second individual port.
 19. Themethod of claim 17, further comprising: establishing, in the secondmode, the loopback path via a switch configured to output to thereceiver, in the first mode, the received signal, and to output to thereceiver, in the second mode, the translated loopback signal.
 20. Themethod of claim 17, wherein the inputting the signal to the receiver inthe first mode is during a first time interval and the inputting thetranslated loopback signal to the receiver in the second mode is duringa second time interval.
 21. The method of claim 17, wherein thewaveguide diplexer is a first waveguide diplexer, the receiver is afirst receiver, and the received signal from the target device is afirst received signal, the method further comprising: receiving, fromthe target device, a receive wave at a common port of a second waveguidediplexer, the second waveguide diplexer having a third individual portassociated with the transmit range and a fourth individual portassociated with the receive frequency range, the second waveguidediplexer outputting a second receive signal within the receive frequencyrange at the fourth individual port of the second waveguide diplexer;and inputting, to a second receiver, the second receive signalconcurrently with inputting the translated loopback signal to the firstreceiver.
 22. The method of claim 21, wherein the first transmit signalis transmitted during a first time interval, and wherein the loopbacksignal is a first loopback signal, the method further comprising:providing a third transmit signal to the third individual port of thesecond waveguide diplexer during a second time interval, the thirdtransmit signal within the first frequency range; coupling a secondloopback signal associated with the third transmit signal from thecommon port of the second waveguide diplexer; translating the secondloopback signal from within the first frequency range to within thesecond frequency range; receiving, using the first receiver, thetranslated second loopback signal; comparing, using the first receiver,the translated second loopback signal with a representation of the thirdtransmit signal; adjusting a fourth transmit signal based at least inpart on the comparison; and providing the adjusted fourth transmitsignal to the second waveguide diplexer for transmission to the targetdevice.
 23. The method of claim 17, wherein the waveguide diplexer is afirst waveguide diplexer, the receiver is a first receiver, the methodfurther comprising: receiving, from the target device, a receive wavewithin the receive frequency range at the common port of the firstwaveguide diplexer, the first waveguide diplexer outputting the receivesignal at the second individual port based at least in part on thereceive wave; coupling the translated loopback signal into a common portof a second waveguide diplexer, the second waveguide diplexer having athird individual port associated with the transmit range and a fourthindividual port associated with the receive frequency range, wherein theloopback path includes a portion of the second waveguide diplexercomprising the common port and the fourth individual port; andinputting, to a second receiver, the receive signal concurrently withinputting the translated loopback signal to the first receiver.
 24. Themethod of claim 17, wherein adjusting the second transmit signalcomprises adjusting a frequency, a phase, a polarity, a symbol rate, aslew rate, a frequency-dependent gain slope, a frequency-dependent phasevariation, a time-dependent transient amplitude, a time-dependenttransient phase, a frequency and amplitude dependentamplitude-modulation, a frequency and amplitude dependent phasemodulation, or a transmit power of the second transmit signal.
 25. Themethod of claim 17, further comprising: storing one or more calibrationvalues based at least in part on the comparison.
 26. The method of claim17, further comprising: entering the second mode in response toreceiving a command.
 27. The method of claim 17, further comprising:determining an availability of the receiver for comparing the translatedloopback signal to the representation of the first transmit signal basedat least in part on a scheduling of communications from the targetdevice; and performing the comparing of the translated loopback signalto the representation of the first transmit signal based at least inpart on the availability.